In 1976, Robert Turner and Rury Holman developed the concept that fasting
plasma insulin and glucose levels were determined, in part, by a hepatic-beta
cell feedback loop [Abstract]. They postulated
that elevated fasting glucose levels reflected a compensatory mechanism
that maintained fasting insulin levels when there was a reduced insulin
secretory capacity, and that fasting insulin levels were elevated in
direct proportion to diminished insulin sensitivity. A mathematical
feedback model based on these hypotheses was constructed to estimate
the degrees of beta cell function and insulin sensitivity that would
equate to the steady state plasma glucose and insulin levels observed
in an individual [Metabolism 1979; 28:1086-96].

In 1985, David Matthews et al published an expanded and more
comprehensive structural model known as the Homeostasis Assessment Model
(HOMA). This model, written in Fortran, took greater account of peripheral
glucose uptake and could use fasting levels of specific insulin or C-peptide
in addition to RIA insulin [Diabetologia 1985; 28(7): 412-9]. As an alternative
to running the Fortran computer model, a set of linear equations
were also made available. These gave approximate values of %B and, instead
of %S, HOMA IR (insulin resistance) which is the reciprocal of %S (100/%S).
The equations have been used widely, particularly for estimates of beta
cell function and insulin resistance in large-scale studies, but are
not appropriate for use with currently available insulin assays.

In 1998, Jonathan Levy et al published an updated HOMA model
(HOMA2) which took account of variations in hepatic and peripheral glucose
resistance, increases in the insulin secretion curve for plasma glucose
concentrations above 10 mmol/L (180 mg/dL) and the contribution of circulating
proinsulin [Diabetes Care 1998; 21: 2191-92]. The model was recalibrated
also to give %B and %S values of 100% in normal young adults when using
currently available assays for insulin, specific insulin or C-peptide.

In 2004, the HOMA Calculator was released. This provides
quick and easy access to the HOMA2 model for researchers who wish to
use model-derived estimates of %B and %S, rather than linear approximations.
It runs on a variety of computer platforms and can be downloaded
from this site.